Key result
A low-salt diet significantly reduced mean arterial pressure in Systemic KO mice compared to a normal-salt diet (114 vs 148 mmHg, P<0.0001), demonstrating that renal AT1 receptor activation promotes hypertension primarily through sodium retention.
Why the study?
Does activation of renal AT1 receptors mediate angiotensin II-dependent hypertension through sodium retention?
Does activation of renal AT1 receptors mediate angiotensin II-dependent hypertension through sodium retention?
Absolute Event Rate: 114% vs 148%
p-value: p=<0.0001
This preclinical study demonstrates that renal AT1 receptors mediate angiotensin II-dependent hypertension primarily through sodium retention, providing mechanistic insight into how AT1 receptor blockade protects against hypertensive kidney disease.
Cautions against clinical changes from animal data; leaves open renal AT1 mechanisms for human hypertension studies.
Activation of type 1 angiotensin II (AT(1)) receptors in the kidney promotes blood pressure elevation and target organ damage, but whether renal AT(1) receptors influence the level of hypertension by stimulating sodium retention or by raising systemic vascular resistance has not been established. In the current studies, we used a kidney cross-transplantation strategy to determine whether increased sodium reabsorption by AT(1) receptors in the kidney mediates the chronic hypertensive response to angiotensin II. We found this to be true. In addition, we also identified a second, nontrivial component of blood pressure elevation induced by activation of renal AT(1) receptors that is sodium-independent. As the kidney has the capacity to limit the transmission of elevated systemic blood pressure into the renal microcirculation, prior studies struggled to clearly discriminate the relative contributions of blood pressure elevation vs. activation of AT(1) receptors to hypertensive kidney injury. In our model, we found that rapid surges in blood pressure, which may overcome the kidney's capacity to prevent perturbations in renal hemodynamics, correlate closely with kidney damage in hypertension. Moreover, maximal kidney injury in hypertension may require activation of a pool of nonrenal, systemic AT(1) receptors. These studies provide insight into precise mechanisms through which AT(1) receptor blockade influences the progression of hypertensive kidney disease.
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Crowley et al. (2011) studied Angiotensin II-dependent hypertension. Low-salt diet (0.01% NaCl) during Angiotensin II infusion vs. Normal-salt diet (0.4% NaCl) was evaluated on Mean arterial pressure averaged over the entire ANG II infusion period (p=<0.0001). A low-salt diet significantly reduced mean arterial pressure in Systemic KO mice compared to a normal-salt diet (114 vs 148 mmHg, P<0.0001), demonstrating that renal AT1 receptor activation promotes hypertension primarily through sodium retention.
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